Internet Explorer 5.5/Outlook Express

When logging onto the Internet, dial up is o.k. – handshake is o.k. – but IE then says it cannot find server, DNS error, and will not display a Web page. Outlook express does pretty much the same, it cannot find the server??
Have re-installed Windows ME, have re-installed Office 2000, but the problem persists!!
The dialler is set correct, would’nt validate otherwise, just will not display Web pages.